1. Field of the Invention
This invention relates to an improved tensioner for an endless power transmission belt or the like and to a method of making such a tensioner.
2. Prior Art Statement
It is known to provide a tensioner for a power transmission belt that is adapted to be operated in an endless path, the belt tensioner comprising a support means for being fixed relative to the belt, a belt engaging means carried by the support means and being movable relative thereto, mechanical spring means operatively associated with the support means and the belt engaging means for urging the belt engaging means relative to the support means and against the belt with a force to tension the belt, and frictional dampening means operatively associated with the support means and the belt engaging means to dampen the movement of the belt engaging means relative to the support means in at least one direction of movement thereof. The dampening means has a longitudinal axis and the support means comprises a shaft means having a longitudinal axis and being fixed from movement relative to the belt engaging means. The belt engaging means has a portion thereof rotatably carried by the shaft means so as to rotate relative to the shaft means. For example, see the U.S. Pat. No. 4,362,525 to Sproul; the U.S. Pat. No. 4,351,636 to Hagger; the U.S. Pat. No. 4,299,584 to Sproul, the U.S. Pat. No. 3,413,866 to Ford, and the U.S. Pat. No. 2,753,724 to Leyer et al.
It is also known to applicant to provide a tensioner for a power transmission belt that is adapted to be operated in an endless path, the tensioner comprising a support means for being fixed relative to the belt, a belt engaging means carried by the support means and being movable relative thereto, mechanical spring means operatively associated with the support means and the belt engaging means for urging the belt engaging means relative to the support means and against the belt with a force to tension the belt, and dampening means operatively associated with the support means and the belt engaging means to dampen the movement of the belt engaging means relative to the support means in at least one direction of movement thereof. The dampening means has a longitudinal axis and the spring means has a longitudinal axis and is spiraled about the axis thereof. The support means comprises a shaft means having a longitudinal axis and is fixed from movement relative to the belt engaging means, the shaft means carrying the dampening means and the spring means in spaced apart side-by-side relation thereon with the axis of the shaft means being substantially coaxial with the axes of the dampening means and the spring means whereby the dampening means and the spring means are coaxially spaced apart and are coaxially aligned by the shaft means. The belt engaging means has a portion thereof disposed between the dampening means and the spring means and is rotatably carried by the shaft means so as to rotate relative to the shaft means whereby the dampening means and the spring means are coaxially spaced apart from each other by the portion of the belt engaging means. For example, see the copending patent application of James K. Brew et al, Ser. No. 581,645, filed Feb. 21, 1984, and the copending patent application of Randy C. Foster, Ser. No. 633,154, filed July 20, 1984.
It was found that in the tensioner as set forth in the aforementioned copending patent application Ser. Nos. 581,645 or 633,154, while having a rotary fluid dampening unit being utilized in connection therewith, the rotary dampening unit additionally frictionally dampened the movement of the belt engaging means relative to the support means because of the friction created between the relatively moving parts thereof and such frictional dampening increased the tighter the parts thereof were forced together during the assembly thereof.
Also, another known tensioner has the torsion spring thereof under axial compression to axially force the belt engaging arm away from the spring housing and against a stationary friction disc surface whereby the side of the belt engaging arm rubs against such friction surface under the force of the torsion spring during movement of the arm relative to the support means of the tensioner for dampening purposes.
It is also known to applicant to provide a tensioner for a power transmission belt that is adapted to be operated in an endless path, the tensioner comprising a support means for being fixed relative to the belt, a belt engaging means carried by the support means and being movable relative thereto, and mechanical spring means operatively associated with the support means and the belt engaging means for urging the belt engaging means relative to the support means and against the belt with a force to tension the belt. The spring means has a longitudinal axis and is spiraled about the axis thereof. The support means comprises a shaft means having a longitudinal axis and is fixed from movement relative to the belt engaging means. The belt engaging means has a portion thereof rotatably carried by the shaft means so as to rotate relative to the shaft means, the portion of the belt engaging means having a slot therein. The spring means has an inner coil provided with an inner end bent at an angle relative to the inner coil and is received in the slot to interconnect the spring means to the portion of the belt engaging means. For example, see the aforementioned two copending patent applications, Ser. Nos. 581,645 and 633,154.